It is often desirable to provide a load-transporting vehicle, such as a truck or trailer, with a self-contained automatic unloading mechanism for mechanically discharging a load from within the vehicle, thereby economizing on labor.
One proposal, for example, comprises a bulkhead or pusher contained within the vehicle body linked to a belt or cable which runs along the bed of the vehicle between front and rear wind-up rolls. For loading the vehicle, the bulkhead would be moved to the front of the vehicle and the vehicle loaded behind the bulkhead. For unloading the vehicle, the belt or cable would be wound onto the rear wind-up roll, which might be situated under the vehicle bed at its rear, whereby the bulkhead pushes the load out the back of the vehicle.
When unloading a vehicle in the above manner onto a loading dock which is substantially level with the bed of the vehicle, it is advantageous to be able to push the load beyond the end of the vehicle and beyond the adjacent edge of the dock so that, for example, if the dock has a doorway, the load can be pushed through the doorway to a position where it is protected from the environment. For this purpose, it is necessary that the bulkhead have a depth (lengthwise of the vehicle) sufficient for its back pushing surface to be moved the required distance beyond the backend of the vehicle. Further, the bulkhead should be linked to the belt or cable only at or near the frontend of the bulkhead to enable the back surface of the bulkhead to be moved beyond the back wind-up roll. With this arrangement, however, when the bulkhead is moved beyond the backend of the vehicle, forces imposed thereon by the load tend to tilt or tip the bulkhead backwards about its front end connection with the belt or cable, resulting in an uneven pushing force on the load in the vertical direction and possible instability of the load to the extent that the pushing operation may have to be terminated before the required load position is obtained. Moreover, if the bulkhead was supported, for example by angled braces extending toward the front of the vehicle, such braces would take up space lengthwise at the front of the vehicle in the loading position of the bulkhead, thereby reducing the loading space available behind the bulkhead.